Not Applicable
Not Applicable
This invention relates to an optical unit comprising several optical elements and a support structure with element supports for receiving the optical elements. The invention furthermore relates to the use of the optical unit.
Within the scope of the present specification, the term xe2x80x9coptical unitxe2x80x9d is intended to mean units with optical elements, such as mirrors and lenses, i.e. reflecting telescopes, for example, and in particular, but not exclusively, so-called skewed reflectors, i.e. reflector telescopes whose mirrors are not arranged coaxially.
Demands for accuracy made on optical units are generally comparatively great. Particular demands are made on optical units which are parts of apparatus used in space. These not only need to meet extensive requirements made on accuracy, but also compatibility requirements demanded in space, which makes achieving great accuracy difficult. In particular, the mass of the optical unit must be as low as possible. Moreover, the optical unit and its fastening on the apparatus must be embodied to be such that its transport into space, which usually takes place by means of a rocket and involves high static loads and vibrations, can be tolerated without damage. Finally, the optical unit and its fastening on the apparatus must be laid out in such a way that the large temperature differences occurring in space, and the steep temperature gradients caused by these temperature differences, have no negative effects on the apparatus and the optical unit. It is possible here for the extremes of temperature to lie far outside the range of customary ambient temperatures.
Up to now, essentially two types of optical units have been known for use in space. With the first type, the optical elements are coaxially arranged and the receiving structure is in the approximate shape of a tube, if necessary with branches, and the optical elements, i.e. the mirror or lens arrangements, are received in this tube, or are enclosed in a dynamically balanced manner by this tube, or the branches of the tube. With the second type, the optical elements are not coaxially arranged, the receiving structure essentially is in the shape of a closed box and the optical elements are fastened to surfaces of this box. The disadvantage of the tube-like, as well as the box-like receiving structures is essentially seen to lie in that they are too heavy. In general, they have a wall thickness which is the same all over and is designed for that element support, which is subjected to the greatest stress, as a result of which the receiving structure for the areas of other, less stressed element supports, is too large. Moreover, the tube-like, as well as the box-like receiving structures are disadvantageous in view of thermal stresses, since they essentially form a closed envelope.
A further disadvantage of the previously known optical units lies in that temperature differences have a negative effect on the precision of the position of optical elements in respect to each other, as well as on the durability of their connection with each other.
It is therefore the object of the invention to provide an optical unit of the type mentioned at the outset, by means of which the disadvantages of the prior art structures can be avoided, propose an optical unit of the type mentioned at the outset, which avoids the problem of heat expansion and to propose a use of the novel optical units in space.
As mentioned, the element support may be fastened on other parts of the receiving structure only along a portion of its rim. This portion can be continuous, so that the element support is fastened in a cantilevered manner, so to speak, or it can consist of a few, for example two, partial areas.
Many advantages can be achieved by the novel embodiment of the receiving structure of the optical unit, and the most important ones of these will be listed in what follows.
Essentially, material is only employed where it is actually needed for reasons of the dimensions of the optical elements. By means of this it is possible to decrease the mass of the receiving structure, and the energy requirements for transporting the apparatus to which the optical unit is attached is thus reduced.
Because of the embodiment of the receiving structure, or the lack of an envelope for the optical unit, their moments of inertia are also reduced, which has the result that the output requirements for tracking by the optical unit are also minimized. If, on the other hand, a defined amount of energy for tracking by the optical unit is provided, the bandwidth of the tracking can be increased, for example.
Moreover, disadvantageous effects of the large temperature differences and temperature gradients can be eliminated or at least reduced to a large degree by means of the temperature elements and the control unit.
Additional element supports can then be embodied similar to the known receiving structures as closed element supports in a tube- or box-shape. Such receiving structures can then be called complex receiving structures.
The element supports are preferably dimensioned not only to match the dimensions and masses of the optical element to be received, but generally to match the stresses to be absorbed, in order to minimize the mass and moments of inertia of the support structure as much as possible.
It has been shown to be practical for this purpose to provide the individual element supports with mass-reducing cutouts, for example bores, and/or with reinforcing attachments, for example ribs, possibly also with beads for increasing stiffness.
The element supports of the novel optical unit can be produced individually and connected with each other by screwing, bolting, riveting, gluing, welding or soldering them together.
In another preferred embodiment of the novel optical unit the receiving structure can be integrally produced, for example, pressed, sintered, cut out of a block, or produced from bent and, if required, deep-drawn plate material.
Every optical element can be fastened directly in the associated element support, for example by cementing or gluing of its element rim to the rim of a recess in the element support intended for receiving the element. It is also possible to provide a suspension for the optical elements.
The characteristics of the first and second embodiment variation of the invention can be combined, from which an optical unit results which in every way is particularly advantageous in mechanical and thermal respects.
Although the optical units in accordance with the invention had been specially conceived for use in space, they can also be employed in other ways. When using the optical units as components of an apparatus in space, the receiving structure is advantageously fastened at least nearly isostatically on the apparatus.
Further properties and advantages of the invention will be extensively described in what follows by means of the description and with reference to the drawings.